feat(config): expose all width heurstic options

Author: calebcartwright

rustfmt-core/rustfmt-config/src/config_type.rs

@@ -96,7 +96,15 @@ macro_rules! create_config {
                     (self.0).$i.1 = true;
                     (self.0).$i.2 = value;
                     match stringify!($i) {
-                        "max_width" | "use_small_heuristics" => self.0.set_heuristics(),
+                        "max_width"
+                        | "width_heuristics"
+                        | "fn_call_width"
+                        | "single_line_if_else_max_width"
+                        | "attr_fn_like_width"
+                        | "struct_lit_width"
+                        | "struct_variant_width"
+                        | "array_width"
+                        | "chain_width" => self.0.set_heuristics(),
                         "license_template_path" => self.0.set_license_template(),
                         &_ => (),
                     }
@@ -228,16 +236,24 @@ macro_rules! create_config {
                 }
 
                 match key {
-                    "max_width" | "use_small_heuristics" => self.set_heuristics(),
+                    "max_width"
+                    | "width_heuristics"
+                    | "fn_call_width"
+                    | "single_line_if_else_max_width"
+                    | "attr_fn_like_width"
+                    | "struct_lit_width"
+                    | "struct_variant_width"
+                    | "array_width"
+                    | "chain_width" => self.set_heuristics(),
                     "license_template_path" => self.set_license_template(),
                     &_ => (),
                 }
             }
 
             #[allow(unreachable_pub)]
             pub fn is_hidden_option(name: &str) -> bool {
-                const HIDE_OPTIONS: [&str; 6] = [
-                    "verbose", "verbose_diff", "file_lines", "width_heuristics",
+                const HIDE_OPTIONS: [&str; 5] = [
+                    "verbose", "verbose_diff", "file_lines",
                     "recursive", "print_misformatted_file_names",
                 ];
                 HIDE_OPTIONS.contains(&name)
@@ -280,16 +296,88 @@ macro_rules! create_config {
                 )+
             }
 
+            fn set_width_heuristics(&mut self, heuristics: WidthHeuristics) {
+                let max_width = self.max_width.2;
+                let get_width_value = |
+                    was_set: bool,
+                    override_value: usize,
+                    heuristic_value: usize,
+                    config_key: &str,
+                | -> usize {
+                    if !was_set {
+                        return heuristic_value;
+                    }
+                    if override_value > max_width {
+                        panic!("`{}` cannot have a value that exceeds `max_width`", config_key);
+                    }
+                    override_value
+                };
+
+                let fn_call_width = get_width_value(
+                    self.was_set().fn_call_width(),
+                    self.fn_call_width.2,
+                    heuristics.fn_call_width,
+                    "fn_call_width",
+                );
+                self.fn_call_width.2 = fn_call_width;
+
+                let attr_fn_like_width = get_width_value(
+                    self.was_set().attr_fn_like_width(),
+                    self.attr_fn_like_width.2,
+                    heuristics.attr_fn_like_width,
+                    "attr_fn_like_width",
+                );
+                self.attr_fn_like_width.2 = attr_fn_like_width;
+
+                let struct_lit_width = get_width_value(
+                    self.was_set().struct_lit_width(),
+                    self.struct_lit_width.2,
+                    heuristics.struct_lit_width,
+                    "struct_lit_width",
+                );
+                self.struct_lit_width.2 = struct_lit_width;
+
+                let struct_variant_width = get_width_value(
+                    self.was_set().struct_variant_width(),
+                    self.struct_variant_width.2,
+                    heuristics.struct_variant_width,
+                    "struct_variant_width",
+                );
+                self.struct_variant_width.2 = struct_variant_width;
+
+                let array_width = get_width_value(
+                    self.was_set().array_width(),
+                    self.array_width.2,
+                    heuristics.array_width,
+                    "array_width",
+                );
+                self.array_width.2 = array_width;
+
+                let chain_width = get_width_value(
+                    self.was_set().chain_width(),
+                    self.chain_width.2,
+                    heuristics.chain_width,
+                    "chain_width",
+                );
+                self.chain_width.2 = chain_width;
+
+                let single_line_if_else_max_width = get_width_value(
+                    self.was_set().single_line_if_else_max_width(),
+                    self.single_line_if_else_max_width.2,
+                    heuristics.single_line_if_else_max_width,
+                    "single_line_if_else_max_width",
+                );
+                self.single_line_if_else_max_width.2 = single_line_if_else_max_width;
+            }
+
             fn set_heuristics(&mut self) {
-                if self.use_small_heuristics.2 == Heuristics::Default {
-                    let max_width = self.max_width.2;
-                    self.set().width_heuristics(WidthHeuristics::scaled(max_width));
-                } else if self.use_small_heuristics.2 == Heuristics::Max {
-                    let max_width = self.max_width.2;
-                    self.set().width_heuristics(WidthHeuristics::set(max_width));
-                } else {
-                    self.set().width_heuristics(WidthHeuristics::null());
-                }
+                let max_width = self.max_width.2;
+                match self.width_heuristics.2 {
+                    Heuristics::Scaled =>
+                        self.set_width_heuristics(WidthHeuristics::scaled(max_width)),
+                    Heuristics::Max => self.set_width_heuristics(WidthHeuristics::set(max_width)),
+                    Heuristics::Off => self.set_width_heuristics(WidthHeuristics::null()),
+                };
             }
 
             fn set_license_template(&mut self) {

rustfmt-core/rustfmt-config/src/lib.rs

@@ -32,9 +32,24 @@ create_config! {
     hard_tabs: bool, false, true, "Use tab characters for indentation, spaces for alignment";
     tab_spaces: usize, 4, true, "Number of spaces per tab";
     newline_style: NewlineStyle, NewlineStyle::Auto, true, "Unix or Windows line endings";
-    use_small_heuristics: Heuristics, Heuristics::Default, true, "Whether to use different \
-        formatting for items and expressions if they satisfy a heuristic notion of 'small'";
     indent_style: IndentStyle, IndentStyle::Block, false, "How do we indent expressions or items";
+    width_heuristics: Heuristics, Heuristics::Scaled, true, "Controls width heuristics \
+        by setting the values for the individual width heuristic options";
+
+    // Width Heuristics
+    fn_call_width: usize, 60, true, "Maximum width of the args of a function call before \
+        falling back to vertical formatting.";
+    attr_fn_like_width: usize, 70, true, "Maximum width of the args of a function-like \
+        attributes before falling back to vertical formatting.";
+    struct_lit_width: usize, 18, true, "Maximum width in the body of a struct lit before \
+        falling back to vertical formatting.";
+    struct_variant_width: usize, 35, true, "Maximum width in the body of a struct variant before \
+        falling back to vertical formatting.";
+    array_width: usize, 60, true,  "Maximum width of an array literal before falling \
+        back to vertical formatting.";
+    chain_width: usize, 60, true, "Maximum length of a chain to fit on a single line.";
+    single_line_if_else_max_width: usize, 50, true, "Maximum line length for single line if-else \
+        expressions. A value of zero means always break if-else expressions.";
 
     // Comments. macros, and strings
     wrap_comments: bool, false, false, "Break comments to fit on the line";
@@ -146,8 +161,6 @@ create_config! {
     file_lines: FileLines, FileLines::all(), false,
         "Lines to format; this is not supported in rustfmt.toml, and can only be specified \
          via the --file-lines option";
-    width_heuristics: WidthHeuristics, WidthHeuristics::scaled(100), false,
-        "'small' heuristic values";
     emit_mode: EmitMode, EmitMode::Files, false,
         "What emit Mode to use when none is supplied";
     print_misformatted_file_names: bool, false, true,
@@ -167,7 +180,6 @@ impl PartialConfig {
         let mut cloned = self.clone();
         cloned.file_lines = None;
         cloned.verbose = None;
-        cloned.width_heuristics = None;
         cloned.print_misformatted_file_names = None;
         cloned.recursive = None;
         cloned.emit_mode = None;
@@ -389,9 +401,6 @@ mod test {
         create_config! {
             // Options that are used by the generated functions
             max_width: usize, 100, true, "Maximum width of each line";
-            use_small_heuristics: Heuristics, Heuristics::Default, true,
-                "Whether to use different formatting for items and \
-                 expressions if they satisfy a heuristic notion of 'small'.";
             license_template_path: String, String::default(), false,
                 "Beginning of file must match license template";
             required_version: String, env!("CARGO_PKG_VERSION").to_owned(), false,
@@ -403,8 +412,22 @@ mod test {
             file_lines: FileLines, FileLines::all(), false,
                 "Lines to format; this is not supported in rustfmt.toml, and can only be specified \
                     via the --file-lines option";
-            width_heuristics: WidthHeuristics, WidthHeuristics::scaled(100), false,
-                "'small' heuristic values";
+            width_heuristics: Heuristics, Heuristics::Scaled, true, "Controls width heuristics \
+                    by setting the values for the individual width heuristic options";
+            // Width Heuristics
+            fn_call_width: usize, 60, true, "Maximum width of the args of a function call before \
+                falling back to vertical formatting.";
+            attr_fn_like_width: usize, 70, true, "Maximum width of the args of a function-like \
+                attributes before falling back to vertical formatting.";
+            struct_lit_width: usize, 18, true, "Maximum width in the body of a struct lit before \
+                falling back to vertical formatting.";
+            struct_variant_width: usize, 35, true, "Maximum width in the body of a struct \
+                variant before falling back to vertical formatting.";
+            array_width: usize, 60, true,  "Maximum width of an array literal before falling \
+                back to vertical formatting.";
+            chain_width: usize, 60, true, "Maximum length of a chain to fit on a single line.";
+            single_line_if_else_max_width: usize, 50, true, "Maximum line length for single \
+                line if-else expressions. A value of zero means always break if-else expressions.";
 
             // Options that are used by the tests
             stable_option: bool, false, true, "A stable option";
@@ -492,8 +515,15 @@ mod test {
 hard_tabs = false
 tab_spaces = 4
 newline_style = "Auto"
-use_small_heuristics = "Default"
 indent_style = "Block"
+width_heuristics = "Scaled"
+fn_call_width = 60
+attr_fn_like_width = 70
+struct_lit_width = 18
+struct_variant_width = 35
+array_width = 60
+chain_width = 60
+single_line_if_else_max_width = 50
 wrap_comments = false
 format_code_in_doc_comments = false
 comment_width = 80

rustfmt-core/rustfmt-config/src/options.rs

@@ -77,14 +77,16 @@ pub enum TypeDensity {
 }
 
 #[config_type]
-/// To what extent does rustfmt pursue its heuristics?
+/// Heuristic settings that can be used to simply
+/// the configuration of the granular width configurations
+/// like `struct_lit_width`, `array_width`, etc.
 pub enum Heuristics {
     /// Turn off any heuristics
     Off,
     /// Turn on max heuristics
     Max,
-    /// Use Rustfmt's defaults
-    Default,
+    /// Use scaled values based on the value of `max_width`
+    Scaled,
 }
 
 impl Density {
@@ -248,14 +250,6 @@ impl WidthHeuristics {
     }
 }
 
-impl std::str::FromStr for WidthHeuristics {
-    type Err = &'static str;
-
-    fn from_str(_: &str) -> Result<Self, Self::Err> {
-        Err("WidthHeuristics is not parsable")
-    }
-}
-
 impl Default for EmitMode {
     fn default() -> EmitMode {
         EmitMode::Files